The present invention relates to an improved screen cloth and to a screen assembly which are used in a vibrating screening machine, and to a method of fabrication thereof.
By way of background, the vibrating screening machines of the type shown in U.S. Pat. No. 4,882,054 and other types of vibratory screening machines utilize screens of the type shown in U.S. Pat. No. 4,575,421 and also use other types of screens which are mounted in various types of frames.
The performance of a screen in a screening operation is determined by a combination of its "conveyance" and "conductance" under given conditions of vibration. Conveyance is the amount of solids or the feed at which the solids are moved or are being advanced forward on the screen during vibration. This is usually measured in inches per minute. Conductance is a measure of how easily the particles which are being screened pass through the screen. A combination of the conveyance and conductance determines the screen performance, and improved performance is usually accompanied by less blinding, that is, less clogging of the screen.
It has been found that if the wires of the screen which contacts the material being screened are toughened, both the conveyance and conductance of the screen are improved and blinding is lessened so that the screen performs better.